Method for separating high-aluminum iron ore by extracting sodium carbonate and sodium sulfate from coke oven desulfurized fly ash

Abstract

The invention relates to a method for separating high-aluminum iron ore by extracting sodium carbonate and sodium sulfate from coke oven desulfurized fly ash, which comprises the following steps: firstly, removing large-particle impurities and organic matters in the desulfurized fly ash by adopting a sieving and high-temperature calcining method, then adjusting the pH value of the solution to remove NaOH, then separating and escaping NaCl clear liquid through nanofiltration, and collecting concentrated liquid containing sodium sulfate and sodium carbonate, and finally, respectively extracting sodium sulfate and sodium carbonate through methods of evaporation concentration, cooling crystallization, evaporation concentration and cooling recrystallization. Sodium sulfate is added during preliminary roasting, and a roasting reduction reaction is carried out at the high temperature of 1000-1100 DEG C, so that dissolution of aluminum is promoted, and dissolution of iron is inhibited. And cooling to room temperature, adding sodium carbonate powder, and carrying out secondary roasting at the temperature of 900-1000 DEG C to promote reduction of iron. Compared with the prior art, the method has the advantages that sodium carbonate and sodium sulfate are successfully extracted from the coke oven desulfurized fly ash, the separation of aluminum and iron is effectively promoted, the coke oven desulfurized fly ash is solved, and the utilization rate of aluminum iron ore resources is improved.

Description

Technical Field

[0001] The invention relates to the technical field of comprehensive utilization of solid waste resources, and in particular to a method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore. Background Art

[0002] Coking is a key process in steelmaking, which mainly converts coal into coke under oxygen-free and high-temperature conditions, and is used as a fuel and reducing agent for blast furnace ironmaking. Due to the particularity of coke oven flue gas (small gas volume, high temperature, and tar content), the most widely used limestone-gypsum wet desulfurization process is not suitable for coke oven flue gas desulfurization. The sodium-based desulfurization process, which is not economical in the power and sintering industries, has been promoted in the coke oven flue gas desulfurization industry due to its advantage of small temperature drop.

[0003] Coke oven desulfurization ash is a byproduct produced in the sodium-based desulfurization process using Na2CO3 or NaHCO3 as a desulfurizer. Its main components are sodium sulfate and some unreacted sodium carbonate, in addition to a small amount of sodium chloride and sodium hydroxide. These components are easily soluble in water, and after being piled or landfilled, they will seep into the soil through rainwater and cause serious pollution. The treatment cost of this first-level hazardous waste is about 1,000 yuan / ton. At present, the treatment technology of coke oven desulfurization ash is not mature at home and abroad, which has become a major challenge facing the coking industry.

[0004] Although there is a method for recovering desulfurization ash, a byproduct of coke oven flue gas desulfurization, such as patent CN110745845A, which is mainly used to treat desulfurization ash using alkali metal salts as desulfurizers, and recover sodium sulfate through adsorption, nanofiltration separation and other steps, it fails to make full use of other components such as sodium carbonate. Another patent CN111422885B is based on mixed salt, preparation method and application of coke oven flue gas desulfurization ash, and describes a method for preparing mixed salt using coke oven desulfurization ash and applying it to the preparation of washing powder, but the safety and market acceptance of converting industrial hazardous waste into daily necessities still need further verification.

[0005] my country has abundant high-aluminum iron ore, in which aluminum-containing minerals and iron-containing minerals are closely symbiotic and intercalated, and a large amount of iron and aluminum coexist in isomorphous forms in the ore. The key to the utilization of such resources is to achieve efficient separation of iron and aluminum. Sodium salt roasting is a common and effective aluminum-iron separation process. By adding sodium salts (such as sodium carbonate, sodium sulfate, etc.) and treating at appropriate temperature and atmosphere, insoluble minerals are converted into soluble sodium salts, and the resulting roasted sand is leached through water, dilute acid or dilute alkaline solution, and aluminum and iron are separated by a dissolution step. In addition, the addition of alkali metal salts and alkaline earth metal oxides can cause iron oxide lattice distortion during the reduction process, accelerate the reduction reaction, and increase the reaction rate. According to CN110408773B, by adding sodium salt solution to the ore powder and roasting and subsequent leaching, aluminum-rich liquid phase and iron-rich solid phase can be effectively separated. The sodium salt used is sodium carbonate or sodium sulfate. However, this technology does not take into account the difference between sodium sulfate and sodium carbonate in the separation of aluminum and iron in high-aluminum iron ore. There are problems such as low iron recovery rate in the separation process and low iron grade in the iron-rich solid phase. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore, solve the problem of secondary pollution caused by the stacking of coke oven desulfurization ash and realize the high value-added resource utilization of coke oven desulfurization ash.

[0007] The purpose of the present invention can be achieved by the following technical scheme: A method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore, comprising the following steps:

[0008] (1) Calcination treatment: The coke oven desulfurization ash is sieved through 200 mesh to remove large particle impurities, and then calcined at a high temperature of 600-800℃ for 1-2 hours to remove organic matter.

[0009] (2) Mixing and stirring: The calcined residue is mixed with deionized water at a mass concentration of 20-25% and stirred thoroughly, and the clear liquid is collected after filtration.

[0010] (3) pH adjustment: Add 1 mol / L dilute sulfuric acid to the clear solution and adjust the pH value to 8-9 to remove NaOH in the solution.

[0011] (4) Nanofiltration separation: Use a nanofiltration membrane to separate the solution and remove the NaCl clear solution, and collect the concentrated solution containing sodium sulfate and sodium carbonate.

[0012] (5) Concentration and saturation: The concentrated solution obtained in step (4) is evaporated and concentrated at 70-90° C. to saturated crystals, and a saturated solution is obtained after centrifugal separation.

[0013] (6) Cooling crystallization: The saturated solution obtained in step (5) is cooled to 10°C-15°C for cooling crystallization, and the sodium carbonate solution and sodium sulfate crystals are separated by filtration. The crystals are centrifuged, washed and dried to obtain sodium sulfate powder.

[0014] (7) Evaporation and recrystallization: The sodium carbonate solution obtained in step (6) is evaporated and concentrated at 70-90° C., then cooled to 20° C. for cooling and crystallization, and then centrifuged, washed and dried to obtain sodium carbonate powder.

[0015] (8) Preliminary calcination: The sodium sulfate powder obtained in step (6) is uniformly mixed with high-aluminum iron ore at a mass fraction of 10-15% to form agglomerates, and then reduction-calcined with bituminous coal at 1000-1100° C. for 40 minutes to promote the dissolution of aluminum and inhibit the dissolution of iron. The mass ratio of sodium sulfate powder to high-aluminum iron ore and bituminous coal is: (10-15):100:25.

[0016] (9) Secondary calcination: After the primary calcined product is cooled to room temperature, 5-15% by mass of the sodium carbonate powder obtained in step (7) is added and calcined at 900-1000° C. for 20 minutes to improve the recovery rate of iron. After cooling, the product is ground through a 200-mesh sieve to obtain calcined powder.

[0017] (10) Alkaline leaching: The calcined powder is added to an alkaline leaching solution (NaOH) for leaching. After the leaching is completed, an aluminum-rich liquid phase and an iron-rich solid phase are obtained by solid-liquid separation.

[0018] Furthermore, the total content of Na2CO3 and Na2SO4 in the coke oven desulfurization ash is ≥90wt%.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention utilizes coke oven desulfurization ash to extract sodium salt, mainly sodium carbonate and sodium sulfate, and uses it as a roasting additive for preparing high-aluminum iron ore, which can improve the reduction efficiency of iron oxides and realize effective separation of iron and aluminum by forming sodium aluminate or sodium aluminosilicate. This method not only solves the problem of coke oven desulfurization ash treatment, but also improves the utilization rate of aluminum iron ore resources.

[0021] 2. The present invention successfully extracts the main components of sodium sulfate (Na2SO4) and sodium carbonate (Na2CO3) from the coke oven desulfurization ash through various methods such as high-temperature calcination, pH value adjustment, nanofiltration separation, evaporation concentration, and cooling crystallization, and effectively removes organic matter, sodium chloride (NaCl), sodium hydroxide (NaOH) and other impurities. This process realizes the resource recovery of coke oven desulfurization ash and reduces environmental pollution.

[0022] 3. The present invention utilizes the special role of sodium salt extracted from coke oven desulfurization ash in the treatment of high-aluminum iron ore to effectively promote the separation of aluminum and iron. It improves the reduction efficiency of iron oxides and realizes the effective separation of iron and aluminum by forming compounds such as sodium aluminate or sodium aluminosilicate, thereby improving the comprehensive utilization rate of aluminum iron ore resources.

[0023] 4. The present invention utilizes the difference in the promoting effect of sodium carbonate and sodium sulfate extracted from coke oven desulfurization ash in aluminum-iron separation, and uses staged roasting. The primary roasting utilizes the characteristics of sodium sulfate to promote the dissolution of aluminum and inhibit the dissolution of iron, thereby ensuring the high grade of iron in the iron-rich solid phase; the secondary roasting utilizes the characteristics of sodium carbonate to promote the reduction of iron and improve the recovery rate of iron. Specifically: a staged roasting method is adopted, roasting additives are reasonably selected, and the roasting temperature and time are adjusted to maximize the chemical properties of sodium sulfate and sodium carbonate. In the primary roasting stage, sodium sulfate is used as an additive to carry out treatment at a higher temperature to promote the dissolution of aluminum and inhibit the dissolution of iron, obtain higher-grade iron and improve the separation rate of aluminum. In the secondary roasting stage, sodium carbonate is used as an additive to gradually reduce the processing temperature, at which time most of the aluminum has been separated, in order to promote the reduction of iron, further optimize the separation effect of aluminum and iron, and improve the recovery rate of iron. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a flow chart of utilizing coke oven desulfurization ash to extract sodium carbonate and sodium sulfate for separation of high-aluminum iron ore. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] The present invention provides a method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore, such as Figure 1 As shown, the specific working steps and principles are as follows:

[0027] (1) Calcination treatment: The coke oven desulfurization ash is sieved through 200 mesh to remove large particle impurities, and then calcined at 700℃ for 1.5 hours to remove organic matter. The total content of Na2CO3 and Na2SO4 in the coke oven desulfurization ash is ≥90wt%

[0028] (2) Mixing and stirring: The calcined residue is mixed with deionized water at a mass concentration of 20-25% and stirred thoroughly, and the clear liquid is collected after filtration.

[0029] (3) pH adjustment: Add dilute sulfuric acid (generally, dilute sulfuric acid with a concentration of 1 mol / L) to the clear solution and adjust the pH value to 8-9 to remove NaOH in the solution.

[0030] (4) Nanofiltration separation: Use a nanofiltration membrane (generally 1-2 nm) to separate the solution and remove the NaCl clear solution, collecting the concentrated solution containing sodium sulfate and sodium carbonate.

[0031] (5) Concentration and saturation: The concentrated solution containing sodium sulfate and sodium carbonate is evaporated and concentrated at 70-90°C to saturated crystals, and a saturated solution is obtained after centrifugal separation.

[0032] (6) Cooling crystallization: The saturated solution is cooled to 10°C-15°C for cooling crystallization, and the sodium carbonate solution and sodium sulfate crystals are separated by filtration. The crystals are centrifuged, washed and dried to obtain sodium sulfate powder.

[0033] (7) Evaporation and recrystallization: The sodium carbonate solution is evaporated and concentrated at 70-90°C, then cooled to 20°C for cooling and crystallization, and sodium carbonate powder is obtained after centrifugal washing and drying.

[0034] (8) Preliminary calcination: Sodium sulfate powder is uniformly mixed with high-aluminum iron ore at a mass fraction of 10-15% to form agglomerates, and then reduction roasted with bituminous coal at 1000-1100°C for 40 minutes. High-aluminum iron ore can come from high-aluminum limonite, and its composition is generally (total iron content is more than 30%, alumina content is more than 10%), and bituminous coal composition is generally (fixed carbon content is not less than 40%). The mass ratio of high-aluminum iron ore to bituminous coal is: 100:25.

[0035] (9) Secondary calcination: After the primary calcined product is cooled to room temperature, 5-15% by mass of sodium carbonate powder is added and calcined at 900-1000°C for 20 minutes. After cooling, the product is ground through a 200 mesh sieve to obtain calcined powder.

[0036] (10) Alkaline leaching: The roasted powder is added to an alkaline leaching solution (10-20 g / L NaOH solution, liquid-to-solid ratio L:kg=10:1) for leaching. After the leaching is completed, an aluminum-rich liquid phase and an iron-rich solid phase are obtained by solid-liquid separation.

[0037] The following is a detailed description through specific examples. Unless otherwise specified, the raw materials and equipment involved in the present invention are all commercially available raw materials and equipment commonly used in the art.

[0038] Example 1: The coke oven desulfurization ash which is a byproduct of the SDS desulfurization system of the coke oven flue gas of a Baosteel was treated. The content of Na2SO4 in the coke oven desulfurization ash was 66.32%, and the content of Na2CO3 was 26.81%.

[0039] The above coke oven desulfurization ash is sieved with 200 mesh to remove large particle impurities, and then calcined at a high temperature of 700°C for 1.5 hours to remove organic matter; the calcined residue is mixed with deionized water at a mass concentration of 20% and fully stirred, filtered and the clear liquid is collected, and dilute sulfuric acid is added to the clear liquid to adjust the pH value to 8-9 to remove NaOH in the solution: the solution is separated using a nanofiltration membrane and the NaCl clear liquid is removed, and the concentrated solution containing sodium sulfate and sodium carbonate is collected. The concentrated solution containing sodium sulfate and sodium carbonate is evaporated and concentrated at 80°C to saturated crystals, and a saturated solution is obtained after centrifugal separation. The obtained saturated solution is cooled to 12°C for cooling crystallization, and the sodium carbonate solution and sodium sulfate crystals are separated by filtration. After the sodium sulfate crystals are centrifuged, washed and dried, sodium sulfate powder is obtained.

[0040] The sodium carbonate solution was evaporated and concentrated at 80°C, then cooled to 20°C for cooling and crystallization, and sodium carbonate powder was obtained after centrifugal washing and drying.

[0041] Sodium sulfate powder is uniformly mixed with high-aluminum iron ore at a mass fraction of 10% to form agglomerates, and then reduction roasted with bituminous coal at 1000-1100° C. for 40 minutes. In this embodiment, the composition of the high-aluminum iron ore is (TFe content 42.31%, Al2O3 content 12.74%), and the fixed carbon content of the bituminous coal is 51.62%. The mass ratio of high-aluminum iron ore to bituminous coal is: 100:25.

[0042] The main reactions that occur during reduction roasting by adding sodium sulfate are:

[0043] Na2SO4+Al2O3+6SiO2+CO==Na2O·Al2O 3· 6SiO2+SO2+CO2

[0044] Na2SO4+Al2O3+4SiO2+CO==Na2O·Al2O 3· 4SiO2+SO2+CO2

[0045] 1 / 4Na2SO4+CO==1 / 4Na2S+CO2

[0046] 1 / 3Na2SO4+CO==1 / 3Na2O+1 / 3S+CO2

[0047] Na2S+FeO+Al2O3==Na2O·Al2O3+FeS

[0048] Na2S+FeO+SiO2==Na2SiO3+FeS

[0049] After the preliminary calcined product is cooled to room temperature, 10% by mass of sodium carbonate powder is added and the product is calcined at 1000° C. for 20 minutes. After cooling, the product is ground through a 200-mesh sieve to obtain calcined powder.

[0050] The main reactions that occur during reduction roasting by adding sodium carbonate are:

[0051] Al2O3+4SiO2+Na2CO3==Na2O·Al2O 3· 4SiO2+CO2

[0052] Al2O3+6SiO2+Na2CO3==Na2O·Al2O 3· 6SiO2+CO2

[0053] The roasted powder is added to an alkaline leaching solution (NaOH) for leaching, and after the leaching is completed, an aluminum-rich liquid phase and an iron-rich solid phase are obtained by solid-liquid separation.

[0054] The obtained aluminum-rich liquid phase and iron-rich solid phase were tested for composition, and the results were as follows: the iron grade in the iron-rich solid phase was 58.07%, the aluminum content was 0.74%, the iron recovery rate was 85.26%, and the aluminum separation rate was 94.19%.

[0055] Example 2: The coke oven desulfurization ash which is a byproduct of the SDS desulfurization system of the coke oven flue gas of a Baosteel was treated. The content of Na2SO4 in the coke oven desulfurization ash was 66.32%, and the content of Na2CO3 was 26.81%.

[0056] The above coke oven desulfurization ash is sieved with 200 mesh to remove large particle impurities, and then calcined at a high temperature of 700°C for 1.5 hours to remove organic matter; the calcined residue is mixed with deionized water at a mass concentration of 20% and fully stirred, filtered and the clear liquid is collected, and dilute sulfuric acid is added to the clear liquid to adjust the pH value to 8-9 to remove NaOH in the solution: the solution is separated using a nanofiltration membrane and the NaCl clear liquid is removed, and the concentrated solution containing sodium sulfate and sodium carbonate is collected. The concentrated solution containing sodium sulfate and sodium carbonate is evaporated and concentrated at 80°C to saturated crystals, and a saturated solution is obtained after centrifugal separation. The obtained saturated solution is cooled to 12°C for cooling crystallization, and the sodium carbonate solution and sodium sulfate crystals are separated by filtration. After the sodium sulfate crystals are centrifuged, washed and dried, sodium sulfate powder is obtained.

[0057] The sodium carbonate solution was evaporated and concentrated at 80°C, then cooled to 20°C for cooling and crystallization, and sodium carbonate powder was obtained after centrifugal washing and drying.

[0058] Sodium sulfate powder is uniformly mixed with high-aluminum iron ore at a mass fraction of 10% to form agglomerates, and then reduction roasted with bituminous coal at 1000-1100° C. for 40 minutes. In this embodiment, the composition of the high-aluminum iron ore is (TFe content 47.85%, Al2O3 content 10.71%), and the fixed carbon content of the bituminous coal is 51.62%. The mass ratio of high-aluminum iron ore to bituminous coal is: 100:25.

[0059] After the preliminary calcined product is cooled to room temperature, 10% by mass of sodium carbonate powder is added and the product is calcined at 1000° C. for 20 minutes. After cooling, the product is ground through a 200-mesh sieve to obtain calcined powder.

[0060] The roasted powder is added to an alkaline leaching solution (NaOH) for leaching, and after the leaching is completed, an aluminum-rich liquid phase and an iron-rich solid phase are obtained by solid-liquid separation.

[0061] The obtained aluminum-rich liquid phase and iron-rich solid phase were tested for composition, and the results were as follows: the iron grade in the iron-rich solid phase was 62.43%, the aluminum content was 0.78%, the iron recovery rate was 84.16%, and the aluminum separation rate was 92.72%.

[0062] Comparative Example 1

[0063] The rest is the same as Example 1, wherein sodium sulfate and sodium carbonate powder are commercially available products, that is, sodium salt is not extracted from coke oven desulfurization ash, and the effects of the two are compared:

[0064] Commercially available sodium sulfate powder is uniformly mixed with high-aluminum iron ore at a mass fraction of 10% to form agglomerates, and then reduction roasted together with bituminous coal at 1000-1100° C. for 40 minutes.

[0065] After the preliminary calcined product is cooled to room temperature, 10% by mass of sodium carbonate powder is added and the product is calcined at 1000° C. for 20 minutes. After cooling, the product is ground through a 200-mesh sieve to obtain calcined powder.

[0066] The roasted powder is added to an alkaline leaching solution (NaOH) for leaching, and after the leaching is completed, an aluminum-rich liquid phase and an iron-rich solid phase are obtained by solid-liquid separation.

[0067] The obtained aluminum-rich liquid phase and iron-rich solid phase were tested for composition, and the results were as follows: the iron grade in the iron-rich solid phase was 60.12%, the aluminum content was 0.81%, the iron recovery rate was 82.35%, and the aluminum separation rate was 93.64%.

[0068] Comparing Example 1 with Comparative Example 1, it can be seen that the sodium salt extracted from the coke oven desulfurization ash is used for separation of high-aluminum iron ore, the iron grade is slightly lower, the iron recovery rate is higher, the iron separation effect is almost the same, but the aluminum separation effect is better.

[0069] Comparative Example 2

[0070] The rest is the same as Example 2, wherein sodium sulfate and sodium carbonate powder are commercially available products, that is, sodium salt is not extracted from coke oven desulfurization ash, and the effects of the two are compared:

[0071] Commercially available sodium sulfate powder is uniformly mixed with high-aluminum iron ore at a mass fraction of 10% to form agglomerates, and then reduction roasted together with bituminous coal at 1000-1100° C. for 40 minutes.

[0072] After the preliminary calcined product is cooled to room temperature, 10% by mass of sodium carbonate powder is added and the product is calcined at 1000° C. for 20 minutes. After cooling, the product is ground through a 200-mesh sieve to obtain calcined powder.

[0073] The roasted powder is added to an alkaline leaching solution (NaOH) for leaching, and after the leaching is completed, an aluminum-rich liquid phase and an iron-rich solid phase are obtained by solid-liquid separation.

[0074] The obtained aluminum-rich liquid phase and iron-rich solid phase were tested for composition, and the results were as follows: the iron grade in the iron-rich solid phase was 67.12%, the aluminum content was 1.04%, the iron recovery rate was 78.28%, and the aluminum separation rate was 90.29%.

[0075] Comparing Example 2 with Comparative Example 2, it can be seen that when sodium salt is extracted from coke oven desulfurization ash for separation of high-aluminum iron ore, the iron grade is slightly lower, the iron recovery rate is higher, the iron separation effect is almost the same, but the aluminum separation effect is better.

[0076] Comparative Example 3

[0077] The rest is the same as Example 1 (high-aluminum iron ore composition), only sodium sulfate powder extracted from coke oven desulfurization ash is used, and it is roasted once without adding sodium carbonate powder or roasting in stages.

[0078] The commercially available sodium carbonate powder is uniformly mixed with high-aluminum iron ore at a mass fraction of 10% to form agglomerates, and then reduction roasted with bituminous coal at 1000-1100°C for 60 minutes, and then ground through a 200-mesh sieve to obtain roasted powder after cooling. The roasted powder is added to an alkaline leaching solution (NaOH) for leaching, and after leaching, an aluminum-rich liquid phase and an iron-rich solid phase are obtained through solid-liquid separation.

[0079] The obtained aluminum-rich liquid phase and iron-rich solid phase were tested for composition, and the results were as follows: the iron grade in the iron-rich solid phase was 56.21%, the aluminum content was 1.21%, the iron recovery rate was 70.81%, and the aluminum separation rate was 90.50%.

[0080] Comparing Example 1 with Comparative Example 3, it can be seen that the sodium carbonate and sodium sulfate extracted from the coke oven desulfurization ash are roasted in stages for separation of high-aluminum iron ore. Compared with the reduction roasting with sodium sulfate alone, the iron grade is slightly improved, the iron recovery rate is significantly increased, and the aluminum separation rate is slightly increased, which improves the aluminum-iron separation effect to a certain extent.

[0081] Comparative Example 4

[0082] The rest is the same as Example 1 (high-aluminum iron ore composition), only sodium carbonate powder extracted from coke oven desulfurization ash is used, and it is roasted once without adding sodium sulfate powder or roasting in stages.

[0083] The commercially available sodium carbonate powder is uniformly mixed with high-aluminum iron ore at a mass fraction of 10% to form agglomerates, and then reduction roasted with bituminous coal at 1000-1100°C for 60 minutes, and then ground through a 200-mesh sieve to obtain roasted powder after cooling. The roasted powder is added to an alkaline leaching solution (NaOH) for leaching, and after leaching, an aluminum-rich liquid phase and an iron-rich solid phase are obtained through solid-liquid separation.

[0084] The obtained aluminum-rich liquid phase and iron-rich solid phase were tested for composition, and the results were as follows: the iron grade in the iron-rich solid phase was 51.06%, the aluminum content was 2.17%, the iron recovery rate was 78.66%, and the aluminum separation rate was 82.97%.

[0085] Comparing Example 1 with Comparative Example 4, it can be seen that the sodium carbonate and sodium sulfate extracted from the coke oven desulfurization ash are roasted in stages for separation of high-aluminum iron ore. Compared with the reduction roasting with sodium carbonate alone, the iron grade is significantly improved, the iron recovery rate is significantly improved, the aluminum separation rate is greatly improved, and the aluminum-iron separation effect is significantly improved.

[0086] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore, characterized in that: The following steps are involved: (1) Calcination treatment: The coke oven desulfurization ash is screened to remove large particles of impurities, and then calcined at high temperature to remove organic matter; (2) Mixing and stirring: Mix the calcined residue with deionized water and stir thoroughly, and collect the clear liquid after filtering; (3) pH adjustment: adjusting the pH value of the clear solution obtained in step (2) to 8-9 to remove NaOH in the solution; (4) Nanofiltration separation: using a nanofiltration membrane to separate the solution obtained in step (3) and remove the NaCl clear solution, and collecting the concentrated solution containing sodium sulfate and sodium carbonate; (5) Concentration and saturation: The concentrated solution obtained in step (4) is evaporated and concentrated to saturated crystals, and a saturated solution is obtained after centrifugal separation; (6) cooling crystallization: cooling the saturated solution obtained in step (5) to perform cooling crystallization, filtering and separating the sodium carbonate solution and sodium sulfate crystals, and washing and drying the sodium sulfate crystals by centrifugation to obtain sodium sulfate powder; (7) Evaporation and recrystallization: The sodium carbonate solution obtained in step (6) is evaporated and concentrated, and then cooled for cooling crystallization, and then centrifuged, washed and dried to obtain sodium carbonate powder; (8) Preliminary calcination: The sodium sulfate powder obtained in step (6) is uniformly mixed with high-aluminum iron ore to form agglomerates, and then reduction-calcined with bituminous coal at 1000-1100° C. for 30-50 minutes to promote the dissolution of aluminum and inhibit the dissolution of iron; (9) secondary roasting: after the primary roasted product is cooled to room temperature, 5-15% by mass of the sodium carbonate powder obtained in step (7) is added, and roasting is continued at 900-1000° C. for 20 minutes to improve the recovery rate of iron. After cooling, the product is ground and sieved to obtain roasted powder; (10) Alkaline leaching: The calcined powder is added to an alkaline leaching solution for leaching. After the leaching is completed, an aluminum-rich liquid phase and an iron-rich solid phase are obtained by solid-liquid separation.

2. The method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore according to claim 1, characterized in that: In step (1), a 200-mesh molecular sieve is used for screening, and the high-temperature calcination temperature is 600-800° C. and the time is 1-2 hours.

3. The method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore according to claim 1, characterized in that: The total content of Na2CO3 and Na2SO4 in the coke oven desulfurization ash in step (1) is ≥90wt%.

4. The method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore according to claim 1, characterized in that: The mass concentration of the solution of the residue after calcination in step (2) mixed with deionized water is 20-25%.

5. The method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore according to claim 1, characterized in that: In step (3), dilute sulfuric acid is used to adjust the pH value.

6. The method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore according to claim 1, characterized in that: The evaporation concentration temperature in step (5) and step (7) is 70-90°C.

7. The method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore according to claim 1, characterized in that: The cooling crystallization temperature in step (6) is 10-15°C.

8. The method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore according to claim 1, characterized in that: The cooling crystallization temperature in step (7) is 20°C.

9. The method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore according to claim 1, characterized in that: In step (8), the mass ratio of sodium sulfate powder to high-aluminum iron ore and bituminous coal is: (10-15):100:

25.

10. The method for extracting sodium carbonate and sodium sulfate from coke oven desulfurization ash for separation of high-aluminum iron ore according to claim 1, characterized in that: In step (9), 200 mesh molecular sieve is used for sieving; The alkaline leaching solution in step (10) is a 10-20 g / L NaOH solution, and the liquid-to-solid ratio L:kg=10:1.

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